WHY ?

I decide to take a real good look at this used General Jointer to understand the high cost of buying one. I am not an expert when it comes to running a jointer, but I do understand what makes a precision machine so nice to own. I am not comparing one jointer to another jointer, or passing any judgements on any brands, this is just about finding out how precise this machine is at this point in time.

 

WHAT AM I LOOKING FOR?

Lets be very clear, I am not a real good Carpenter, or furniture maker, but for me the precision of a machine can have a major influence on the final product. Like anything that is produced, there are many way and tools to accomplish the task at hand. Repeatability and accuracy may be what you expect out of your equipment, and the question should be, are they capable of it. So what am I looking for in this jointer? The area that will be look at are the in-feed table, out-feed table, and the in-feed to the out-feed tables. This is a lightly used 6″ wide, with a 42′ bed length, Canadian made, 1180 jointer with an age of about 10-15 years. The machine will be completely checked as it sits, and if any adjustments are need, they will be done after all measurements are recorded.

THE IN-FEED TABLE

The in-feed table need to be checked for overall flatness. Utilizing two of the scraped blocks I made (see Bridgeport rebuild ) and a short straight edge, I constructed a bridge to take measurements of the inside surface (closes to the fence). Checking the indicator readings as the Starret surface gauge was slid from one end of the in-feed table to the other, showed how little the table varied. To my surprise it had a total of .001 variation. Next the bridge was moved to the outer edge of the in-feed table where the measurements showed the same .001 variation. I was confident the surface was extremely flat, so I set up the indicator directly to the in-feed table, which showed a very true surface with a variation of .0015 total. Just a note about why I constructed a bridge first to check the surface of the table. Lets suppose the surface of the table had a consistent arc to it, and the surface gauge and indicator were set up and moved along taking measurements, the indicator would only show the variation of the arc, not whether the table was flat. To see if the table is actually flat, it needs to be compared to a know flat surface. The straight edge was previously scraped to a surface plate so it is definitely flat. Once the straight edge is set on the two blocks which have been qualified, the in-feed table can be compared to the bottom edge of the straight edge. Moving the bridge to different locations, gives a better picture of the table surface. Since the table was very consistent to the bridge, I was able to set the surface gauge directly on the table and check some points I could not reach because the bridge was an obstruction. Hopefully this is not to confusing.

 

 

 

 

 

 

THE OUT-FEED TABLE

The out-feed table was checked in the same manor as the in-feed table. There was less than .001 variation on the dial indicator when comparing the out-feed table surface to the bottom of the straight edge which was mounted on blocks. I check the left side and right side of the table with this set up. The out-feed table was swept with the surface gauge on the surface and had .0005 variation. On this last check I set the surface gauge in the middle of the table and extended the rod and indicator so it would reach the end of the table. The surface gauge was then moved so that the indicator could take reading at the left and right edges. The gauge was the rotated 180*, while leaving it in the center position, and the left and right readings were recorded. What I was looking for were edges that rose or fell at the ends, possibly from the grinding process as the wheel entered and exited the cut. The .0005 variations at the end was exceptional.

IN-FEED TO OUT-FEED

The tables need to be checked to one another for parallelism. We know the two tables will be adjusted to different heights while jointing, so we need to verify the two table surfaces travel in the same horizontal plane. This need to be checked in a variety of positions. If the tables stay parallel no matter where they are positioned, we know the angles of the base and tables are in good standing. The two tables need to be set to the same height. The indicator is zeroed to the in-feed table, then the surface gauge is move so the indicator is touching the out-feed table. I choose to adjust the in-feed table in order to set the table height.